Conventionally, an apparatus in which, when an engine revolution number (an engine speed) is reduced due to a start of the coast stop control and a drain pressure from an engine driven mechanical oil pump is reduced, an electrically driven oil pump is driven and a hydraulic pressure to pulleys and clutches is secured has been disclosed (for example, refer to a Patent Document 1).
This Patent Document 1 discloses that, in the continuously variable transmission with a sub transmission, during the coast stop control in which a driving force source is stopped in a traveling state of the vehicle, a speed ratio (a transmission gear ratio) of the continuously variable transmission is prevented from being upshifted toward a higher side than the speed ratio when the coast stop control is started. In this Patent Document 1, while a drive start of the electrically driven oil pump, the hydraulic pressure of a primary pulley is made approximate zero so that a lowest speed ratio is achieved in a balance pressure control and, thereafter, the coast stop control is ended.
However, in the conventional apparatus, when the electrically driven oil pump is abolished, the hydraulic pressure is not generated during the coast stop control. In a state in which the hydraulic pressure cannot be supplied to a secondary pulley, the lowest speed ratio is maintained (inhibit of a high shift). Because of this, there is a case where, even if a hydraulic pressure command value of the primary pulley is made zero, when the hydraulic pressure is supplied from the oil pump in response to a re-start of the engine at a time of a vehicular start, an actual pressure does not become zero dependent upon a situation of valves or so forth, the hydraulic pressure is supplied to the primary pulley, and the lowest speed ratio cannot be maintained.
In this way, when going through the coast stop control (when the vehicle is started), the hydraulic pressure is supplied to the primary pulley. At this time, the speed ratio is shifted toward the high speed ratio side without balancing at the lowest speed ratio. Thus, such a problem is raised that, due to a fact that the hydraulic pressure required for the vehicular start is used for the high shift, an engagement of a starting clutch is delayed, a reduction of the driving force due to the high shift is generated, and a vehicular starting performance is reduced.